Dendritic excitations govern back-propagation via a spike-rate accelerometer
Pojeong Park, J. David Wong-Campos, Daniel G. Itkis, Byung Hun Lee, Yitong Qi, Hunter C. Davis, Benjamin Antin, Amol Pasarkar, Jonathan B. Grimm, Sarah E. Plutkis, Katie L. Holland, Liam Paninski, Luke D. Lavis, Adam E. Cohen
Abstract
Dendrites on neurons support electrical excitations, but the computational significance of these events is not well understood. We developed molecular, optical, and computational tools for all-optical electrophysiology in dendrites. We mapped sub-millisecond voltage dynamics throughout the dendritic trees of CA1 pyramidal neurons under diverse optogenetic and synaptic stimulus patterns, in acute brain slices. Our data show history-dependent spike back-propagation in distal dendrites, driven by locally generated Na+ spikes (dSpikes). Dendritic depolarization created a transient window for dSpike propagation, opened by A-type KV channel inactivation, and closed by slow NaV inactivation. Collisions of dSpikes with synaptic inputs triggered calcium channel and N-methyl-D-aspartate receptor (NMDAR)-dependent dendritic plateau potentials and accompanying complex spikes at the soma. This hierarchical ion channel network acts as a spike-rate accelerometer, providing an intuitive picture connecting dendritic biophysics to associative plasticity rules. Neural mechanisms mediating information flow and processing in dendrites are not fully understood. Here the authors developed techniques to map bioelectrical excitations in the dendrites of neurons in acute slices of mouse brain tissue. They developed a holistic picture of the roles of dendritic excitations in spike back-propagation.